According to
G. E. Moore, "
Goodness is a simple, undefinable, non-natural
property." To call goodness "non-natural" does not mean that it is
supernatural or
divine. It does mean, however, that goodness cannot be reduced to natural properties such as needs, wants or pleasures. Moore also stated that a reduction of ethical properties to a divine command would be the same as stating their naturalness. This would be an example of what he referred to as "the
naturalistic fallacy." Moore claimed that goodness is "
indefinable", i.e., it cannot be defined in any other terms. This is the central claim of non-naturalism. Thus, the meaning of sentences containing the word "good" cannot be explained entirely in terms of sentences not containing the word "good." One cannot substitute words referring to
pleasure, needs or anything else in place of "good." Some properties, such as hardness, roundness and dampness, are clearly natural properties. We encounter them in the real world and can
perceive them. On the other hand, other properties, such as being good and being right, are not so obvious. A great novel is considered to be a good thing; goodness may be said to be a property of that novel. Paying one's debts and telling the truth are generally held to be right things to do; rightness may be said to be a property of certain human
actions. However, these two types of property are quite different. Those natural properties, such as hardness and roundness, can be perceived and encountered in the real world. On the other hand, it is not immediately clear how to physically see, touch or measure the goodness of a novel or the rightness of an action. ==A difficult question==